The present invention relates to container filling machines and, more particularly, to a filler valve assembly for dispensing a liquid into containers that are placed against the filler valve.
Container filling machines typically include a plurality of filler valve assemblies that dispense liquid into individual containers as they pass under the valve assemblies. The filler valve assemblies usually include a filler tube that extends into the interior of the container to be filled when the container is aligned with the filler valve. The filler valve assembly may include a central plunger or piston that is moveable axially within the filler tube to open and close the valve. See e.g., U.S. Pat. No. 5,564,481 to Clxc3xcsserath and U.S. Pat. No. 6,152,195 to Persenaire.
As shown in the above-referenced patents, the central plunger or piston seats against the inner wall of the filler tube to close the valve and prevent liquid from exiting the filler tube. Such valves typically include separate gaskets on one or both of the filler tube and plunger/piston to seal the filler valve when it is closed. Over time, such gaskets wear or can become otherwise damaged such that they may be dislodged from their seats in the valve. This can create a particular problem if the gasket is discharged into a container that is being filled by the valve. If a gasket is determined to be missing, the production line must be shut down. The containers filled during that production run are examined in an attempt to locate the missing gasket and to ensure that a container containing the gasket does not find its way to the consuming public, where it could possibly be ingested. Such inspections are time consuming and frequently unsuccessful, which could result in the unnecessary disposal of filled containers in order to avoid the possibility of tainted product.
Accordingly, it is an object of the present invention to provide a filler valve assembly in which the outlet of the filler tube is effectively sealed without the use of separate gaskets that could be dislodged from the filler valve.
This object, as well as others which will become apparent upon reference to the following detailed description and accompanying drawings, is accomplished by a filler valve assembly that includes a first housing member with an elongated hollow filler tube secured thereto, the filler tube having an outlet through which liquid exits when filling containers. A second housing member having an elongated piston with an enlarged end portion secured thereto is provided so that the elongated piston is disposed interior of the filler tube. The piston is axially moveable with respect to the filler tube to move the enlarged portion of the piston from a first, closed position in which the enlarged portion engages the outlet of the filler tube to block the flow of liquid out from the filler tube, and a second, open position in which the enlarged portion is spaced away from the outlet of the filler tube to permit the flow of liquid out from the filler tube. When in the closed position, a substantially liquid-tight seal is formed between the outlet of the filler tube and the enlarged portion of the piston, both the outlet and the enlarged portion being formed of a metal so that the seal is formed solely by metal-to-metal contact.
Preferably, the enlarged portion of the piston has a shoulder formed at an angle, and the outlet of the filler tube has an internal relief formed at a similar angle, so that, when in the closed position, the seal is formed by the engagement of the shoulder on the piston with the relief on the filler tube outlet. In the preferred embodiment, the angle is 17 degrees.
In another aspect of the invention, the enlarged portion of the piston is made of a metal that is relatively harder than the metal comprising the outlet of the filler tube.